Snakeskin on a fishing line was the instrument used to extract elements of what could be a rudimentary language among wild chimpanzees in Uganda. The tricksy experimental design enabled them to see what alarm call combinations chimps made when a "snake" was on the loose, and if the specific order of calls elicited a different response. The researchers found that sounds were especially effective when you got the order right, potentially demonstrating that syntax exists within wild primates.
The discovery was made by researchers at the University of Zurich, who were aware of two call types among chimps: waa-barks and alarm-huus. A waa-bark signals other chimps to come help out, while alarm-huus are made when an individual gets a nasty shock.
To test if the way these calls were combined altered chimp behavior, the researchers ran a series of snake presentation and call playback tests. They say never work with children or animals, and if you’re already working with animals surely throwing a snake in the mix is only going to complicate things.
So, for ease and ethics, they instead pranked the chimps with a fake snake made up of the skin of a dead python (Python sebae) attached to a fishing line so it could move, like a cat toy. The fake snake was then deployed in front of wild chimps to see what sounds they made and it was observed that they were combining calls and that the type of combination influenced the response of others.
In playback tests, researchers played either solo waa-barks, alarm-huus, or some combination of the sounds together to observe how this altered their alertness. They saw that more chimps joined the “caller” when a waa-bark was followed by an alarm-huus, which was the combination that also triggered the strongest response in terms of looking duration.
This kind of communication is critical to chimpanzees as snakes are a potentially fatal threat to these animals, but are very good at blending into the environment. As such, sounding the alarm can keep the troop safe, and knowing to listen out for certain calls can be a matter of life and death.
That a specific combination of calls appears to elicit the strongest response in these wild animals has fascinating implications for our understanding of language, as it seems the meaning is strongest when the right “phrases” are deployed together. The researchers compare it to a human saying “danger” and “come here”.
“Our findings reported here are also intriguing since they bear striking resemblance with compositional syntactic structures, a core hallmark of language, where the meaning of larger phrases is derived from the meaning of the individual parts,” they wrote.
“These results indicate receivers did not simply respond to each call independently, but rather they seemed to extract a specific meaning from the call combination (/recruitment to a threat/) derived through combining the information encoded in both individual calls.”
Exactly how the combination influences the meaning of the individual's calls isn’t known, as it could be saying two things at once or a means of increasing the urgency of one. In either case, the study authors concluded that it demonstrates the use of call combination in our closest living relative, and suggests “the foundations of syntax may be evolutionarily ancient and present in more simple forms in the last common ancestor of chimpanzees and humans.”
So, who’s taking the hominine for tea?
The study is published in Nature Communications.